The present invention relates to an automatic fuel pump switch unit for a fuel-injected internal combustion engine and particularly to an automatic fuel pump switch unit which automatically controls the activation of the fuel pump operation in accordance with the rotational speed of the engine.
Fuel-injected internal combustion engines may employ a motor-driven fuel pump for supplying pressurized fuel to the various injectors. The injectors may be solenoid-controlled so as to inject the pressurized fuel into the intake manifold passageways for precisely controlled periods at repetition rates which are precisely related to the engine RPM. Or the injectors may be mechanically controlled in such a manner as to merely control or vary the flow rate of an uninterrupted injection of fuel into the intake air stream.
Fuel-injected racing engines may employ injectors which will not inject fuel until a supply of pressurized fuel is available. Conversely, these same injectors may not stop injecting fuel until the pressurized fuel supply is cut off. Such racing engines may thus require the race driver to manually turn on the fuel pump at the proper instant during starting, and conversely, to turn off the fuel pump immediately upon stopping the engine.
Although race drivers become skilled in the technique of turning on the fuel pump at the proper moment, various difficulties and malfunctions may occur if any significant timing errors are made. For example, if the fuel pump is turned on prior to the starting of the engine, flooding of the engine may occur. If the fuel pump is not turned on at the time of starting of an engine which already has adequate initial fuel in the manifold passageways for starting, this can lead to a lean-burn condition and destruction of the engine can result. Other problems are also present in the operation of driver controlled fuel pump systems. Racing drivers are normally required to use a safety tether switch which is connected to positively kill the engine ignition system in the event that the driver is thrown from the boat. In case of such an accident, however, the fuel pump may, of course, continue to operate, unless specially connected to the engine tether switch circuit. If a fuel line also ruptures as a result of an accident, a serious fire hazard may be created if the fuel pump continues to run indefinitely. With the above arrangement, the driver is also required to positively turn off the fuel pump during refueling, and after refueling reinitiate the precise turn-on of the fuel pump during the engine restarting procedure.